The Total Access Communication System (TACS) and the Advanced Mobile Phone Services (AMPS) mobile phone systems provide a three out of five voting arrangement on data received by the mobile phone, this data being, e.g., the Forward Control Channel (FOCC) data or Forward Voice Channel (FVC) data, which is sent from a base station in frames containing data blocks that are repeated at least five consecutive times. This 3/5 voting may be performed in a straight forward way, e.g., by a microprocessor which stores five received data blocks in a memory and then performs a voting procedure on all received five data blocks in accordance with a code or algorithm stored in the processor program memory. The voting and coding may also be performed mainly by hardware when the data blocks are stored in registers, and the above mentioned algorithm is performed by logic circuits.
In a copending U.S. patent application (Ser. No. 07/823,167), titled "Method and circuit for performing 3/5 major voting", the inventors have presented a new and inventive arrangement which performs the voting process in logic hardware, which in a preferred form contains only two data registers to store relevant data. The present invention in its preferred form utilizes this new voting arrangement. The present invention is, however, not limited to the above-mentioned 3/5 voting arrangement, as a person skilled in the art can devise other suitable voting arrangements to operate as the voting block of the present invention.
There are commercially available modem circuits that perform 3/5 voting and decoding of messages, i.e., of data blocks. These modem arrangements do not keep track of which data block is currently received, i.e., they do not indicate to the mobile phone's controlling microprocessor whether the received data block is the first block or any other consecutive block. This will cause a problem on the voice channel, when a multiframe message, such as for example, when a Calling Line Identification (CLI) message is sent from a land station to a mobile station.
The start of the CLI frame or other multiframe message, i.e., the start of control information data, is detected in the mobile phone when a synchronization word is received. The mobile phone can then use a timer to indicate the end of a frame. However, the timer is not very exact, and thus timing may be lost, resulting in lost information. The main objective of the present invention is thus to provide an accurate and reliable arrangement for indicating data blocks in frame, which obviates the above mentioned problem.